Workflow Evansville

Temporary Chlorine Changes

Twice a year – in spring and summer – the Evansville Water and Sewer Utility (EWSU) temporarily changes the disinfectant used in the water treatment process to help keep water mains clean and free of potentially harmful bacteria.

For the water disinfection process, EWSU alternates between two chemicals – chloramine and free chlorine. Customers are notified of the chemical switch in advance of the change. Both chlorine and chloramine are safe for people and animals. 

While the change does not affect most customers, precautions should be taken for individuals going through kidney dialysis and owners of fish tanks and ponds, as well as for select businesses. See more details below.  

Free Chlorine and Chloramine

State drinking water guidelines recommend that utilities using chloramine periodically switch to free chlorine for a while. The temporary use of chlorine ensures that a proper level of disinfectant is maintained throughout the network of water mains and pipes that deliver your drinking water.


EWSU has used chloramine as the primary disinfectant in our water treatment process since 1999. Chloramine, which is comprised of chlorine and ammonia, removes bacteria and viruses that can make you sick. Chloramine creates fewer byproducts, has less smell than chlorine and remains in the distribution system longer to prevent bacterial growth.

Free Chlorine

Free chlorine is a slightly more potent disinfectant than chloramine. It is used to remove more resistant bacteria and viruses that may be found in the water distribution system. Switching to free chlorine is a proactive step to ensure that EWSU maintains optimal disinfectant levels in our water distribution system. 

Impacts to the Look and Taste of Your Water

You may notice a slight change in the taste or smell of your tap water after the change in disinfectants. Free chlorine may have more of a chemical smell, slightly like that of swimming pool water. Each customer has his or her sensitivity level to the taste or smell of free chlorine. Many detect no change at all. The mild chlorine taste and smell are typical and pose no health risk.

The drinking water is regularly monitored to ensure that the water delivered meets or exceeds federal Safe Drinking Water Act standards.    

Are Free Chlorine and Chloraminated Water Safe?

Both chlorine and chloramine are effective and safe for people and animals for drinking, cooking, bathing, watering the garden, and all other standard uses. Most customers will not need to take any precautions as the water remains safe to drink and is treated according to state and federal standards.

However, precautions should be taken to remove or neutralize chloramine and free chlorine during the kidney dialysis process, in the preparation of water for fish tanks and ponds, and for businesses requiring highly processed water. A dechlorination procedure optimized for chloramine removal will work equally well with free chlorine.

People and businesses that typically take special precautions to remove chloramine from tap water (such as dialysis centers, medical facilities and aquatic pet owners) should continue to take the same precautions during the temporary switch from chloramine to free chlorine.

Information for Kidney Dialysis Patients

Just like chloramines, free chlorine must be removed from water used in kidney dialysis machines. EWSU contacts representatives from the medical community to inform them of this temporary conversion. We advise customers who are dialysis patients to call their physicians or dialysis centers if there are any questions.

Information for Fish Owners

Like chloramine, free chlorine is toxic to fish. It is critical for fish owners to remove chlorine, ammonia and chloramine from water used by tropical fish. Local pet stores carry water conditioners that remove chloramine and free chlorine. If you have questions, contact your pet store for information and detailed instructions.